Note: Descriptions are shown in the official language in which they were submitted.
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OPTICAL COMMUNICATION DEVICE, SYSTEM AND METHOD
Field of the Invention
This invention relates to communications devices. In particular, this
invention relates to an optical communications device particularly suitable
for adverse
environments.
E3ackyound of the Invention
Many industrial activities are carried on in environments unfavourable for
human workers. For example, in underwater environments, these activities
include
mining, oil exploration and extraction, installation of telecommunications
cables etc.
Mining in particular is a highly labour intensive activity, especially in an
underwater
environment because of the increased resistance to movement in water,
potential
health problems associated with persistent or prolonged deep-sea diving, and
the
cumbersome equipment required to enable workers to remain submerged for long
periods of time.
Such industrial activities invariably benefit from automation, in both
reduced labour costs and increased productivity. In land-based mining it is
known to
provide robotic mining equipment controlled by radio frequency (rf)
communications.
This enables a relatively small number of workers to remotely control heavy
machinery and equipment located in or on a surface mine (for example in open
pit
mining). There are benefits to avoiding reliance on rf communications for land-
based
mining, such as to avoid interference from other signals, or to alleviate the
need for
approval for use of regulated bandwidths. The benefits of automation in
underwater
activities could potentially be significantly greater, because of the reduced
mobility of
workers operating when submersed.
However, conventional communications methods are often unsuitable for
supporting high bandwidth communications in certain environments, such as an
underwater environment. especially for the control of robotic equipment which
requires the exchange of relatively high data rates with a low error rate for
the wireless
transmission of multiple video signals. Electromagnetic radiation at radio
frequencies
travels poorly through water due to rapid absorption and attenuation. which
severely
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limits the ability to provide ongoing communications between a land- or
surface-based
control centre and submersed robotic equipment used in activities such as
underwater
mining.
Moreover, submersed robotic equipment can be very complex and difficult
to operate. requiring a number of fine movements to guide and operate the
equipment
with the precision necessary for mining and other underwater applications. The
observational skills and dexterity required to effectively operate such
equipment is
substantial and using conventional control systems requires sipificant
training and
experience, particularly when the operator is remote from the equipment.
It would accordingly be advantageous to provide a communications system
for guiding and operating equipment and machinery in unfavourable
environments,
such as underwater environments, which is reliable, fast, and capable of high
data
rates for use in activities such as underwater mining.
=Brief Description of the Drawings
is In drawings which illustrate by way of example only an embodiment of
the
invention,
Figure I is a plan view of a first embodiment of an optical communication
device according to the invention.
Figure 2 is a perspective view of the optical communication device
according of Figure I.
Figure 3 is a side view of the optical communication device of Figure 1.
Figure 4 is a perspective view of another embodiment of an optical
communication device according of the invention.
Figure 5 is a plan view of another embodiment of an optical
communication device according to the invention.
Figure 6 is a side view of two optical communication devices according to
the invention positioned back-to-back.
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CA 02677585 2009-09-03
Figure 7 is a schematic diagram of the LED trigger circuit of the optical
communication device of the embodiment of Figure 1.
Figure 8 is a block diagram of an LED trigger circuit for the optical
communication device of the invention.
Figure 9 is a schematic perspective view of an underwater communications
zone utilizing optical communication devices according to the invention
suspended
from buoys.
Figure 10 is a schematic perspective view of a terrestrial communications
zone utilizing typical optical communication devices according to the
invention on
supports.
Figure 11 is a schematic perspective view of an underwater
communications zone utilizing typical optical communication devices according
to
the invention suspended from a buoy in a chain.
Detailed Description of the Invention
The present invention provides an underwater optical communications
system and method, which is particularly suitable for use in communications
with
mobile robotics and automated equipment and machinery. The present invention
is
particularly suitable for any underwater, terrestrial or space environment
where
localized communication for (dc-operated robotics is required.
The present invention provides an optical receiver or transceiver
comprising, a plurality of light receiving elements positioned to receive
light from a
plurality of directions, comprising a first light receiving element adapted to
output an
electric signal only in response to light of a selected first wavelength or
range of
wavelengths, and at least a second light receiving element adapted to output
an
electric signal only in response to light of a selected second wavelength or
range of
wavelengths different from the first wavelength or range of wavelengths,
whereby the
optical receiver or transceiver can simultaneously receive data independently
in at
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least first and second optical signals respectively having the tirst and
second
wavelength or range of wavelengths.
The present invention provides an optical transceiver comprising a
plurality of light emitting elements positioned so the optical transceiver
emits light in
a plurality of directions, and a plurality of light receiving elements
positioned so the
optical transceiver receives light from a plurality of directions, the light
receiving
elements being interspersed with light transmitting elements.
Figures 1-3 illustrate a first embodiment of the optical communication
device, or optical transceiver 10, of the present invention. It will be
appreciated that
to while the light-emitting face 12 of the optical transceiver 10 of the
first embodiment
has multiple facets 14 for emitting light in a variety of directions, the
number,
orientation and size of facets 14 may vary to optimize the distribution of
light emitted.
For example, the face 12 of the optical transceiver 10 may alternatively be
flat or
dome shaped.
Each facet 14 of the optical transceiver 10 may comprise a facet board 20
with a series of light emitting elements 22, for example light emitting diodes
(LEDs)
22. These facet boards 20, which may for example be formed from heat resistant
circuit board wafers, are attached to a support structure (not shown), such as
a plastic
frame. It will be appreciated that the number and configuration of the light
emitting
elements 22 on each board 20 may vary to optimize the distribution of light
emitted by
the optical transceiver 10. As illustrated in Figures 1 to 3, the optical
transceiver of
this embodiment has eight trapezoidal facet boards 20 and one octagonal top
plate 15.
The top plate 15 has four holes (not shown) to which are affixed optical
receivers.
The optical transceiver 10 of the present invention preferably emits light in
the visible spectrum, via LEDs or any other suitable light emitting element
22. The
precise wavelengths may be selected based on the attenuation characteristics
of the
environment, and may be achieved by selection of the light-emitting elements
22
and/or by optical filtering. By way of example only, certain wavelengths of
green light
in the range around 5,100 to 5,200 Angstroms have been found to travel well
through
seawater. Wavelengths of red light in the range of 6,200 to 7,500 Angstroms
have
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been found to travel well in terrestrial environments, notwithstanding the
ambient
light present. The particular wavelength and intensity of light most suitable
for
terrestrial optical communication may depend upon the transmissivity of the
water or
air, the type of suspension (e.g. organic, sedimentary, dust etc.) causing any
cloudiness
or murkiness or haze, and the spectral characteristics of ambient light within
the
communications zone. However, the particular wavelengths (use of more than one
wavelength of light can be advantageous, as described below) and intensity of
the
light-emitting elements 22, can be optimized through experimentation,
In a preferred configuration of the optical transceiver 10 of the invention,
in each of the facet hoards 20 the number of light emitting elements 22
increases
towards the base 18 of the optical transceiver 10, corresponding to the
dimensions of
the particular facet board 20. In the embodiment shown, each trapezoidal board
20
may have 144 LEDs 22 which draws approximately 1 amp at 50% duty cycle of 10
MHz. Preferably, the face plate 26 also has 144 LEDs 22. The number of LEDs 22
may vary, depending upon the desired optical output of the device 10.
In the embodiment shown in Figure 1, the optical transceiver 10 emits light
over a range of 180'. A total of 360 of light distribution can be achieved by
coupling
two optical transceivers 10 back-to-back in the manner illustrated in Figure
6. It will
be appreciated that each optical transceiver 10 could alternatively be
configured to
have many more facets 14 with boards 20 affixed thereto and if desired opposed
light
emitting faces (equivalent to the two devices 10 shown in Figure 6) so as to
emit light
in all directions (i.e. 360').
Mirrors 40 may be attached to the base 18 to reflect and direct light
emitted from the LEDs 22 out of the light emitting face of the optical
transceiver 10,
to enhance the light emitted. This further helps to distribute the light
emitted out of
the light emitting face and can compensate for any decrease in light emitting
elements
22 due to occlusion caused by detector modules 32 fixed to the face plate 26.
The
mirrors 40 help to reduce the effect of gaps between the facet boards 20. The
mirrors
41 may be configured to have a shape complementary to the shape of the
adjacent
facet board 20, to optimize the amount reflected while still maintaining
sufficient light
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emission over the desired 180c range of the device 10 shown. Mirrors 40 and 41
may
be angled to reflect light out of the light emitting face with a desired
pattern or
dispersion. In the embodiment shown, the mirrors 40 and 41 can increase the
light
transmission efficiency out of the light-emitting face (i.e. in the forward
direction) by
about 20%.
The optical tranceiver 10 also functions to detect light transmitted from a
complementary optical communication device. Detector modules 32 comprise
optical
receiving elements 30. each for example comprising an avalanche photodiode
(APD),
that may be coupled to the optical transceiver 10 to receive light emitted
from other
optical transceivers 10 or from other types of optical beacons (not shown). In
the first
embodiment. four detector modules 32 are used, however it will be appreciated
that
this number may vary.
The optical receiving elements 30 contained within the detector modules
32 may comprise any detector sensitive to the particular wavelength(s) of
light
selected for the light emitting elements 22.
In the embodiment shown in Figures 1, 2 and 3, each detector module 32
comprises a casing 34 connected by screws (not shown) to the comers of the
face plate
26 of the optical transceiver 10. The casing 34 includes the optical receiving
element
30 recessed in an opening 38 at the apex of a concave reflective channeling
dish 39 to
focus the incoming light directly at the optical receiving element 30 to
maximize the
light received. By recessing the optical receiving element 30 in this manner,
the light
emitted from the optical transceiver 10 does not add to the ambient light or
optical
'noise' affecting the sensitivity of the optical receiving element 30.
In another embodiment, shown in Figure 4, detector modules 32 are
coupled to the face plate 26 and also to the interstitual spacing between the
facet
boards 20 bearing the light emitting elements 22. In this configuration, the
detector
modules 32 receive light signals over a range of 180'. .A total of 360' of
light
reception can be achieved by coupling two optical transceivers 10 back-to-back
in the
manner illustrated in Figure 6. In another embodiment, shown in Figure 5, a
number
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of optical receiving elements 30 are included in one larger detector module 32
mounted in a hole (not shown) in the center of the face plate 26.
Each detector module 32 is also positioned with its optical axis face away
from the light emitting elements 22 to reduce opportunities fifr light from
the light
emitting elements 22 striking the optical receiving elements 30. Additional
light
emitting elements 22 may be disposed on the plate 15, tbr example between the
detector modules 32 in the embodiment of Figures I to 4 or distributed about
the
detector module 32 in the embodiment of Figure 5.
Reducing ambient light or optical 'noise' from the device 10 itself may
to also be achieved by interspersing the optical receiving elements 30
amongst the light
emitting elements 22 (not shown), wherein the optical receiving elements 30
are set
back or recessed into the interstitial spacing between the light emitting
elements 22, or
otherwise shielded so that light emitted by the optical transceiver 10 does
not add to
the ambient light or optical 'noise' affecting the sensitivity of the optical
receiving
elements 30.
The detector modules 32, or light receiving elements 30, may bear filters
37 or a similar means of selective filtering to restrict the light received by
each light
receiving element 30 to a particular wavelength or range of wavelengths within
the
visible spectrum. In this manner, different light receiving elements 30 on the
same
optical transceiver 10 may receive light signals of different predetermined
frequencies
or wavelengths emitted from other optical communication devices. By
configuring the
light receiving elements 30 to receive multiplexed optical signals, the data
reception
capability of the optical transceiver 10 increases as a factor of the
multiplexing
capacity of the light receiving elements 30 coupled to the optical transceiver
10. By
using filters 37 or a similar means of selective filtering to restrict the
light received by
each light receiving element 30 to a discrete wavelength or wavelengths within
the
visible spectrum, the required guard bands may be minimized. For example, with
accurate filtering, the guard bands may be reduced to one angstrom in width.
The
wavelengths of light available for data transfer for a given environment may
be
maximized in this manner, and the data transfer capacity may be expressed as a
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function of the effective wavelengths available through filtering in a given
medium,
minus the guard bands required, multiplied by the effective bit rate.
The light receiving elements 30 may be coupled to light sensing circuitry
50, which may have a sensitivity threshold, for example using a Schmidt
trigger
comparator or other comparator to establish a base light level below which the
light
receiving elements 30 do not register a light pulse, which can be set
according to the
average and/or peak ambient light levels within the communications zone 100.
This
maximizes reliability of the communications system, ensuring that the light
receiving
elements 30 are not saturated by ambient light so that all received light
pulses
generated from other optical transceivers 10 will be processed as
communications
signals.
A transparent transceiver dome 16 may be used to enclose the optical
transceiver 10, including all electronics. The dome 16 may be made of glass or
plexiglass, or a similar material, that minimizes diffusion and reflection of
emitted
and incoming light. The dome 16 protects the instrumentation from the external
environment, such as the water when used for underwater environments, and also
from the accumulation of dust or dirt for terrestrial applications or in other
environments. The dome 16 may have a waterproof seal 17, for example a rubber
gasket, around its base 18 coupled to the casing of the optical transceiver 10
and may
be bolted to a base plate 19.
Power may be provided through a battery pack (not shown) either located
in the optical transceiver 10 or external to the dome 16 and connected via
cables 62
through a hole 64 in the base plate 19 of the optical transceiver 10. Cables
62 can also
he used Ibr data transmission through such a hole 64.
The facet board 20 of the optical transceiver 10 of the embodiments
illustrated is based on a Complex Programmable Logic Device (CPLD) 72 with
sufficient power to be capable of driving several loads synchronously. The
input
signal from the Ethernet media converter 74 is fanned out to various LED
trigger
circuits 70 on each LED board 20, preferably through one CPLD 72. The optical
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transceiver 10 may include any number of LED boards 20, each comprising a
plurality
of LED trigger circuits 70.
Suitable LED trigger circuits 70, as illustrated in Figure 7, activate a
plurality of LEDs 22 connected in parallel on one facet board 20. Preferably,
each
LED trigger circuit 70 activates two LEDs 22 connected in parallel as shown.
In its
quiescent state there is no signal at the input of the Schmitt trigger
inverter 76, so the
inverter output is high and there is no voltage drop across the LEDs 22. The
LEDs 22
are illuminated when a trigger signal, which may be in the range of 3.3 to 5.2
volts,
transmitted from the CPLD 72 to the input of the Schmitt trigger inverter 76
in the
LED trigger circuit 70. The output of the Schmitt trigger inverter 76 goes low
for the
duration of the trigger signal, creating a voltage drop across the LEDs 22
resulting in a
current passing from the power source (not shown) through resistors 78
connected in
series with the LEDs 22 and illuminating the LEDs 22. A connection to ground
79
prevents current from -flowing into the Schmitt trigger inverter 76, which
could
damage the component.
This design is preferable over designs which trigger several LEDs 22
connected in series through the base of an RF transistor. With LEDs 22
connected in
series, approximately 45 V power supply was needed to reliably switch 7 LEDs
22,
and due to the competing speed-power output of transistors, such a circuit
could not
be operated at the desired 10 MHz frequency frequency. The LED trigger circuit
70
shown in Figure 7 is capable of switching at 10 MHz and operates at +5V. The
higher
LED trigger speed allows for faster data transfer.
The trigger signal is generated by Ethernet media converter 74, which may
tor example be a commercially available Ethernet media converter designed for
inter-
conversion of I OBaseT and fiber optic signals, modified to exploit its
electrical inputs
and outputs of the fiber optic channel. The Ethernet media converter 74
comprises an
analog-to-digital converter (ADC) and an IP protocal converter for generating
an IP-
based signal from the digital output of the ADC. It will be appreciated that
the
Ethernet media converter 74, which is based on statistical network protocols,
may be
substituted by a media converter based on deterministic network protocols.
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Ethernet hub 82 preferably communicates with an on-board IP-based
camera 83. or any internal or external IP-based device, and a remote
controller
comprising a processing device, for example personal computer (PC) 85 and
associated controls 87.
The electronics internal and external to the optical transceiver 10 are
shown in Figure 8 for one channel of incoming light signals. When the optical
transceiver 10 is configured to receive multiplexed optical signals through
the use of
optical filters 37 over the detector modules 32, or a similar means of
selective filtering
to render each light receiving element 30 reactive to a particular wavelength
or range
of wavelengths within the visible spectrum, similar electronics to those shown
in
Figure 8 may be used for each channel of light.
Preferably. the APD readout electronics 80 comprises the following
components: (a) an APD module 32 comprising a bias power supply with
temperature
compensation, a transimpedance amplifier and a capacitor to filter the output
signal; a
summing amplifier 84; and a wide dynamic range automatic gain amplifier 86.
One
embodiment of the invention utilizes a transimpedance amplifier chip (not
shown)
from Analog Devices, an APD bias supply (not shown) from Matsusada Precision,
and APD sensors 30 from Hamamatsu Corporation. An APD module 32 with only a
APD bias supply and transimpedance amplifier may also be used, such as is
commercially available from Hamamatsu Corporation. It will be appreciated that
similar devices may be obtained from other sources to accomplish the similar
result.
The summing amplifier 84 sums the output voltages from all the
transimpedance amplifiers connected to individual sensors 30 or optical
receiving
elements 30 where multiple API) modules 32 are used. The output of the summing
amplifier is transmitted to the automatic gain amplifier 86, which includes a
filter
module or notch filter to minimize mismatching and filter unwanted low and
high
frequencies. The output of the automatic gain amplifier 86 is at a
predetermined fixed
voltage, preferably around 2.5 to 5 volts, and is thus independent of the
intensity of
light received by the light receiving elements 30.
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based distribution board 72 for activating the plurality of LEDs 22 via
trigger circuits
70 in each LED board 20.In the embodiment shown the digital output of the
Ethernet
media converter 74 is also sent to an Ethernet hub or switch 82 and on to PC
85 which
contains software for managing and controlling the electronic circuitry and
monitoring the data flow.
This design has enabled operation of the optical transceiver 10 in a wide
dynamic range without using logarithmic amplifiers, which are prone to large
drifts
with small changes in operating parameters. There are many devices and systems
for
converting electrical pulses to discrete optical pulses, and for converting
optical
pulses to discrete electrical pulses, in the analogue and digital domains,
which are
well known to those skilled in the art. There are also optical communications
systems
described in the art, some of which are free space communications systems and
some
of which include multiplexing systems for achieving higher data rates, by way
of non-
limiting example only, the System and Method for Free Space Optical
Communications Using Time Division Multiplexing of Digital Communication
Signals described in U.S. Patent No. 6,246,498 issued to Dishman et al. on
June 12,
2001; the Optical Space Communication Apparatus Sending Main Signals and an
Auxiliary Signal for Controlling the Intensity at the Receiver described in
U.S. Patent
No. 5,610,748 issued to Sakanaka et al. on March 11, 1997; and the Optical
Communications System described in U.S. Patent No. 5,896,211 issued to
Watanabe
on April 20, 1999. The invention is not intended to be limited to any
particular opto-
electric conversion methodology, multiplexing scheme or communications system.
Using for example wavelength division multiplexing (WDM), data rates of
10Mb/s or even higher can be achieved by present techniques for a single
wavelength
of light. In the first embodiment of the invention described above, each
transceiving
element 22 transmits light at a discrete wavelength, for example in the green
portion
of the visible light spectrum. By using various frequencies of light in this
fashion, as
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long as the band separation is sufficient multi-directional communications can
occur
simultaneously without interference, thus enhancing the communications speed.
Moreover, as the frequency increases, both the data rate and the directional
sensitivity
of the optical receivers 30 increases.
Figure 9 illustrates a communications zone 100 in an underwater optical
communications system in which the optical transceivers 10 of the present
invention
may be used both as fixed beacon transceivers and as mobile transceivers.
Figure 10
illustrates a communications zone 100 in terrestrial optical communications
system in
which the optical transceivers 10 of the present invention may be used and
affixed to a
surface vehicle 124. It will be appreciated that the principles of the
invention can also
be applied to other water, surface and space-based communications systems.
Further,
although the communications system described herein is advantageously used in
underwater or terrestrial mining applications, it can also be used for such
tasks as
border security (marine patrol), underwater inspection of boat hulls,
inspection of
water intake pipes, and many other applications.
The communications zone 100 is defined by optical transceivers 10 which
are preferably dispersed generally uniformly throughout the communications
zone
100. For underwater optical communications systems, the optical transceivers
10 may
for example be buoyant and affixed to anchors (not shown) set on the floor of
a body
of water, or may be suspended from a boat or other buoyant object 102 floating
on the
water's surface, as illustrated in Figures 9 and 11.
Figure 9 illustrates a 'single cell' communications zone, in which the
communications zone is defined between 'directional corner beacons each
comprising
a single optical communications device 10. The invention also provides a
'multiple-
cell' embodiment in which the communications zone 100 comprises a matrix of
interior optical transceivers 10 and peripheral optical transceivers 10
creating a
network of optical transceivers 10. The optical transceivers 10 in the
interior of the
communications zone 100 are fully multi-directional, and may for example be
spherical embodiments of the optical communications device, or may be the
optical
communications device 10 as shown adjoined as illustrated in Figure 6, by way
of
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CA 02677585 2016-04-19
example only. A description of an optical communications zone may be found in
international application no. PCT/CA2005/000027 published July 28, 2005.
Even in the 'single cell' communications zone embodiment illustrated in
Figure 9, the optical transceivers 10 operating at the periphery of the
communications
zone 100 may instead be fully multi-directional, so that the communications
zone 100
extends for some distance beyond the optical transceivers 10. It will be
appreciated
that it is possible to utilize peripheral optical transceivers 10 that are
directional and
emit light only toward the communications zone 100 as shown in Figures 9 and
10, in
which case the communications zone 100 will not extend substantially beyond
the
peripheral optical transceivers 10. The optical transceivers 10 may be
interconnected
through a network, or may all be connected directly to a control station at
which PC
85 is located.
The submersible craft 120 and the control station each comprise suitable
electro-optical circuitry for converting optical data signals received by the
optical
transceivers 10 from the submersible craft 120 to electrical signals for
controlling the
craft 120, and for converting electrical control signals generated by the
control station
to optical signals transmitted by the optical transceivers 10 to the
submersible craft
120. The light signals emitted by the light emitting elements 22 or may be
modulated
in any suitable fashion.
Figure 9 illustrates a submersible craft 120 which, like the optical
transceivers 10, is provided with at least one optical transceiver 10. The
craft 120
illustrated has one optical transceiver 10 such as the optical transceiver 10
of Figures
1 to 5. The optical transceivers 10 are dispersed about the communications
zone 100
such that the submersible craft 120 is able to receive optical signals
containing
communication data from one or more optical transceivers 10 at all times, and
to send
optical communication data to one or more optical transceivers 10 at all
times,
regardless of the orientation of the craft 120 and regardless of the position
of the craft
120 within the communications zone 100. The optical transceivers 10 are spaced
closely enough to ensure that, within the communications zone 100, the
submersible
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craft 120 is always in optical communication with at least one optical
transceivers 10,
and operate in a "hand-off" tashion similar to that used in cellular telephone
systems,
in which as the telephone transceiver moves from one cell to the next the
cellular
tower which the telephone transceiver is approaching establishes a
communications
link with the transceiver and the cellular tower from which the transceiver is
receding
cuts off its communications link.
At the same time, the optical transceivers 10 are preferably spaced far
enough apart that they do not significantly interfere with the ability of the
submersible
craft 120 to manoeuvre through the communications zone 100. The ideal spacing
may
depend upon many factors, including the intensity of the light emitting
elements 22,
the sensitivity of the light receiving elements 30, the transmissivity of the
water
(including the particular cause of any cloudiness or murkiness), and ambient
light
levels within the communications zone 100.
It is also advantageous to space the optical transceivers 10 so that the
is submersible craft 120 is always in optical communication with at least
three optical
transceivers to. This will allow for positioning and locating the submersible
craft 120
by triangulation.
The optical transceivers 10 may also be located at varying elevations, to
support triangulation for positioning/locating the submersible craft 120
vertically. For
example, Figure 11 illustrates a communications zone 100 defined by a series
of
optical transceivers 10 suspended from a floating buoy 102. The suspended
optical
transceivers 10, which may be powered by a generator (not shown) or battery
(not
shown) on board the buoy 102, may be directional, or may comprise optical
transceivers 10 configured in pairs as in Figure 6 so as to emit light in all
directions.
The optical transceivers 10 are spaced closely enough to ensure that, within
the
communications zone 100, the submersible craft 120 is always in optical
communication with at least one optical transceiver 10.
The optical transceivers 10 may be powered by battery 71 as described
above, or by an electrical generator (not shown) contained in a land-based
control
centre or a or surface-based control centre such as a floating watercraft or
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communications relay buoy, and connected to the optical transceivers 10 by
optical
fibres or electrical cables (not shown). The submersible craft 120 may be
powered by
any suitable means. The control centre and the submersible craft 120 would in
the
first embodiment of the invention each comprise computers, an optical
switching
system, and an on-board Transmit/Receive link, each of which may be of
conventional or any suitable design which is well known to those skilled in
the art. By
way of example only such a system is described in U.S. Patent No. 4,905,309
issued
February 27, 1990 to Maisonneuve et at.
The communications methodology may comprise any conventional optical
communications system, but preferably utilizes a packet-based system utilizing
optical pulses to transmit the data packets. The first embodiment of the
invention
described above operates under a token passing system, in which each token is
managed by a header and footer. Data, preferably including video from on-board
cameras 83 located about the submersible craft 120, is transmitted optically
from the
on-board optical transceiver(s) 10 to the optical transceivers 10 about the
communications zone 100. Data 132 and video information 134 are displayed at
the
control station for monitoring each submersible craft 120, and the return data
stream
132 controls the submersible craft 120, steering it to a new position or
orientation
and/or initiating a task.
Figure 11 illustrates a vertical communications zone 100 for the invention,
in which a number of optical transceivers 10 may be suspended in sequence. The
vertical communications zone 100 may be suspended from buoy 102 with a water-
tight, buoyant casing that also supports a Global Positioning System (GPS)
antenna
(not shown) and circuitry for precise positioning information and
triangulation of the
positions of the submersible craft 120, and optionally a solar cell (not
shown) for
primary or auxiliary power and battery recharging. The casing contains the
power
supply 71 for powering suspended optical transceivers 10; the electro-optical
circuitry
for converting optical signals to electrical control signals and vice versa
for
communications between the suspended optical transceivers 10 and the
submersible
crafts 120; and control circuitry for operating a second communications link,
for
example a radio frequency (RF) transceiver (not shown) coupled between the
electro-
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and transmitting signals to a remote control station (provided for example on
a as a
ship or land-based structure) and thus allowing the submersible crafts 120 to
be
controlled from any desired distance from the communications zone 100.
It will be appreciated that the communications system and method of the
invention can be used solely to control the submersible craft 120 within the
communications zone 100. in which case the craft 120 does not need to be
equipped
with light emitting elements 22 and the optical transceivers 10 about the
communications zone 100 do not need to be equipped with light receiving
elements
30. However, preferably the system and method of the invention provides for bi-
directional including communications from the craft 120 to the optical
transceivers 10
about the communications zone 100, I'm example video transmissions, radar
and/or
sonar telemetry transmissions and the like, in which case both the optical
transceivers
10 about the communications zone 100 and the craft 120 will be equipped with
light
emitting elements 22 and light receiving elements 30, respectively.
IS The control station may comprise a conventional display (not shown)
for
displaying a signal sent by cameras 122 on-board the submersible craft I 20,
and any
suitable control interface, for example a computer 85, allowing the operator
to control
the submersible craft 120 and its equipment through command signals
transmitted to
the optical transceivers 10 about the communications zone 100, and thus to the
submersible craft 120. Where multiple submersible crafts 120 are used, each
submersible craft 120 has a unique address and the packets in the digital data
signals
132 (for example in IP protocol) comprise the address of the particular
submersible
craft 120 for which the command is intended, for example in the packet header,
so
that only the intended submersible craft 120 reacts to the command. Similarly,
data
signals 132 transmitted by each submersible craft 120 comprise the address of
the
particular submersible craft 120 transmitting the data 132, so that the
control centre
recognizes the source of the transmission.
Preferably the invention incorporates bit error rate testing and other
techniques to ensure the integrity of the optical communications. Also, to
reduce the
lu likelihood of the loss of a craft 120 or land vehicle 124 in the event
of a
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CA 02677585 2009-09-03
communications interruption, preferably the submersible craft 120 is designed
to
automatically stop and sink to the bottom of the body of water and the land
vehicle
124 is designed to brake to a stop.
Various embodiments of the present invention having been thus described
in detail by way of example, it will be apparent to those skilled in the art
that
variations and modifications may be made without departing from the invention.
The
invention includes all such variations and modifications as fall within the
scope of the
appended claims.
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